Solution:
We have finished our home work just now. because sentence is in present perfect tense.

Solution:
We use 'am', 'are', 'is' + the -ing form of the verb with present continuous tense. 'Look' word suggest the sentence to be in present form.

Solution:
The pronoun that can be used in place of 'The committee' can be 'their' or 'its'. 'Their' is used in case of living things and 'its' is used in case of non-living things. 'Their' is the correct answer.

Solution:
To tell the time 'past' word is usually used. Half past eight means 30 minutes past eight. 30 minutes is half of an hour.

Solution:
Sentence is in Future perfect tense and active voice. Rule : Subject + modal verb + have/has + V3 + other agents.You should have taken permission of your parents before taking this important decision.

Solution:
"The" is a definite article which is used before a noun that is fixed, special or discussed earlier. "A/An" is used before an indefinite singular noun. "Union leader" is a fixed noun. Hence "the" will be used.He is the union leader.

Solution:
You use if in conditional sentences to introduce the circumstances in which an event or situation might happen, might be happening, or might have happened. Example: She gets very upset if I exclude her.